1. Field of the Invention
This invention relates to a light-emitting diode device, more particularly to a semiconductor light-emitting diode device including a multi-functional layer.
2. Description of the Related Art
Referring to FIG. 1, a conventional semiconductor light-emitting diode device includes a substrate 11, a buffer layer 12, a n-type cladding layer 13, an active layer 14, a p-type cladding layer 15, a current spreading layer 16, a p-type electrode 17, and an n-type electrode 18 formed on an exposed portion of the n-type cladding layer 13. When a working voltage is applied to the semiconductor light-emitting diode device through the p-type and n-type electrodes 17, 18, light resulting from recombination of electrons and holes in the active layer 14 is generated. However, the light emitted upwardly and toward the p-type electrode 17 is blocked by the p-type electrode 17. In addition, a bottom of the p-type electrode 17 which is usually made from a light-absorbing material may absorb the light, thereby decreasing the light output power and light-emitting efficiency.
Referring to FIG. 2, for improvement over the aforesaid semiconductor light-emitting diode device, a semiconductor light-emitting diode device having a structure similar to that of the conventional semiconductor light-emitting diode device is further provided with a reflective layer 19 which is formed within the current spreading layer 16, and is as large as the p-type electrode 17. The reflective layer 19 includes at least two sub-layers made from different materials. A top sub-layer of the reflective layer 19 is made of a conductive material and a bottom sub-layer of the reflective layer 19 is made of an insulating material having light reflectivity. The p-type electrode 17 is disposed over the reflective layer 19. The reflective layer 19 is provided for reflecting light emitted from the active layer 14 below the p-type electrode 17. However, since the reflective layer 19 is provided with a size as large as the p-type electrode 17, a sidelight (indicated by the arrow A) can not be reflected by the reflective layer 19 and is absorbed by the p-type electrode 17. Moreover, when the p-type electrode 17 deviates from the reflective layer 19 during manufacturing, the light emitted from the active layer 14 below the p-type electrode 17 is still absorbed by the p-type electrode 17. Therefore, alignment of the p-type electrode 17 with the reflective layer 19 is required to be precise. Incase of disalignment, the current from the p-type electrode 17 can flow through the current spreading layer 16 to a region of the active layer 14 beneath the p-type electrode 17, thereby reducing the effect of spreading the current flow.